In electrophotographic color printers, so-called tandem-type color printers have become the mainstream, in which photosensitive drums corresponding to colors of yellow, magenta, cyan, and black, are arranged in parallel.
Among these tandem-type color printers, Japanese Patent Application Publication No. 2007-313033 discloses a printer in which process cartridges corresponding to the respective colors as a whole are detachably attached to the main unit of the printer. Each of the process cartridges includes a photosensitive drum and a developer which are contained together in a case for each color. The process cartridges of the respective colors are placed on a tray which is detachably attached to the main unit. On a side of the tray, intermediate electric contacts corresponding to the respective process cartridges are provided. In a state that the process cartridges are placed on the tray, the cartridge electric contact of each process cartridge is connected to the corresponding intermediate electric contact. The printer main unit includes main-unit electric contacts to be connected to the respective intermediate electric contacts in a state that the tray has been attached to the main unit. The respective cartridge electric contacts and the respective intermediate electric contacts are mechanically connected, and the respective intermediate electric contacts and the main-unit electric contacts are mechanically connected at the same time. As a result, the respective cartridge electric contacts and the respective main-unit electric contacts are electrically connected through the respective intermediate electric contacts. In the state that the respective cartridge electric contacts and the main-unit electric contacts are electrically connected, power can be supplied from the main unit to the respective process cartridges.
However, the structure of the tray side becomes complicated when the above intermediate electric contacts are provided.
Therefore, an object of the present invention is to provide a tandem-type process unit having a simple structure.